Although I haven't used my 6SE for some months I wanted to give it a quick bench run to make sure everything was ok.

I did a pretend one star alignment, the first time was all fine and the goto's looked about right but when I slewed the scope away from the alignment "star" using the direction buttons it went into an uncontrolled azimuth rotation and didn't respond to the hand controller (+ model)at all. I had to switch off and start again.

Now it seems to occasionally do this uncontrolled slewing even prior to any alignment and will also do the same thing in azimuth. Always seem to be when moving in the same directions i.e. anticlockwise (az)and in depression (alt), also the sound of the motors doesn't seem as regular when this happens, this despite being run from mains power with a tight fitting adaptor.

My first suggestion would be to try putting fresh, brand new batteries in the base and see what happens. The fact that the connector is tight is not necessarily an indication that it's the right connector and will make a good connection.

The correct size connector is 5.5mm exterior and 2.1mm interior. There is another connector standard which is 5.5mm exterior and 2.5mm interior. It looks almost identical to the right one, but the interior may not make a reliable connection.

If you install batteries in the base, then if the mains connection is weak, the batteries will take over.

If you already have batteries in the base, replace them with brand new ones. What happens sometimes is that you may think you're running off mains, but due to a poor connection are actually running off the batteries, which may now be weak.

I'll second Dans suggestion...mainly because 90 percent of the problems you will encounter with the scope can be and will be traced directly to a power problem...

And for gosh sakes do not use rechargeable AA's to run the scope ...not unless you like to see it dance all over the sky and not respond to your commands.. Rechargeables are however fine to use as a backup power supply if you run with an external battery..

Try prying apart the pins a bit on the male connector in the base for a tighter fit between the female and male connectors. Also, once you do this anchor the cord to the handset arm in front of the connector so that as the mount rotates it does not tug on the connectors.

As advised I did fit a set of unused AA batteries (which I'd never bothered with before) and after my quick test this morning initially I thought the problem seemed fixed but after a period of only a few minutes use the problem returned, but not quite with its previous frequency.

I did notice the HC reports an error message "no response 16" when it happens and sometimes goes blank, but the intermittent nature of the problem does seem to point to an electrical connection problem rather than software or mechanical.

I'll pursue all of the options suggested (I don't have a Lance Armstrong wrist band they don't fit anything anymore, but I do have a nice Bob Marley one somewhere)including a new set of batteries.

If you're now convinced that you do not have a power supply problem, (particularly since you've tried both an external and internal source to little avail), Mike Swanson has the following to say on the subject of "No Response 16/17 Error" in his book "The Nexstar User's Guide".

Note that the book is now of course somewhat dated and he refers to this error in respect of the then Nexstar 5i and 8i which, at the time, shared the same mount, but I still believe his advice applies to the current 6SE/8SE mount.

To quote therefore what he has to say on the matter:

Quote:

"For the Nexstar 5i/8i, open the battery cover and remove the four screws securing the base cover. Carefully lift the base cover, noting that there is a cable running from the battery holder to the base.

Remove and reseat all connector cables attached to the circuit boards.

Be VERY careful not to misalign the pins and the connectors or damage may result.

Sure, it smacks more of engineering than astronomy, but then you are obviously more than capable of carrying it out and think what satisfaction you WILL get when that loose wiring proves to be the cause !

But seriously, approached methodically, it shouldn't be too difficult a task. Let's just hope that it will be successful.

However, I've just been re-reading your initial post in order to recap and came to the conclusion that perhaps one or two issues need a little further clarification.

1) I note (now) that you have a "Plus" HC. Is this the HC version which was originally supplied with the 'scope ?

2) Have you, (at all), inspected the azimuth axis for free movement by trying to rock it manually from side to side ? You shouldn't be able to move it more than a couple of millimetres in either direction.

Similarly, you say that the altitude axis has a tendency to depress when slewing. Have you checked that this is not a side issue and the fact that the OTA has this tendency to drop, is not caused by a loose-ish clutch ?

This is easily checked by taking the OTA to the Zenith and then bringing it down smartly, under full slew power, to the horizontal.

At this point, if you release the HC direction button, the OTA should stop pretty well, dead. Any tendency to drop further however, will indicate a need for clutch adjustment.

My apologies for obvious straw grabbing, Chris, but some answers here might just help to clear my mind as to where we might go from here .

It is interesting that the frequency is reduced. Not sure what would account for that. You said you dismantled the base and checked for loose connections. Since you're capable of that, may I suggest one more thing? Dismantle once again, and for each connector, remove it and replace it several times. If connectors sit for a while they can sometimes develop a layer of oxides which can interfere with the connection. If you plug/unplug several times, the contacts will scrape off the oxide and make a better connection.

Thanks for the advice I'll try these options tomorrow (with a clear space to store all of those screws)starting with the reset Tel, fingers crossed...but I'm sure with all of this knowledge we'll beat the bug into submission.

You are truly a Nexstar wizard. I reset to factory condition, re-input the settings (except the backlash which I wanted to refine anyway) and have just put the scope through some vigorous slews at maximum speed.

About 300° in az and 180° in alt, which would definitely have resulted in it throwing a tantrum...but it works perfectly, touch wood, it's as well behaved as Rolls Royce.

It is odd that the "bug" arose in the first place, I've never done anything clever like reflashing the handset, in fact I don't have a connector for the USB's on either of my computers - wish Celestron would sort that one out with new scopes.

Perhaps not Chris, I assure you; any heroics demanded and I'm the first to run !

The only thing I believe I ever had in common with Shane was his height. He was reported to be about 5'4" wasn't he ? Indeed, rumour had it,that he, (Alan Ladd that is), had either to stand on a box to kiss the heroine or she had to stand in a hole. :rofl2:

But as to the reason for the problem, let's just hope there's no repetition !